This would probably be the best option, compared to a grocery delivery. Check out Supreme Transportation in Orlando. 10 stars!
We used Magical Vacation Services for our last trip and although he did not add crazy mark-up, he made a lot of substitutions we did not ask for. We did learn that the specific items and brands were available. I guess he just got what was easiest. We were very specific in our shopping list and still ended up with things we did not want. We ended up throwing away about $30 - $40 of it. Not happy!
Dizzy Dolphin will also substitute without your approval, even when you ask them not to. They have about 60% mark-up on many items, plus a delivery fee and they ask for a tip.
If you can get everything at one place, either Costco or a local grocery store, that would be your best bet.